The objective of this research is to study what metabolite(s) mediate(s) the signal, where the receptor system is located and the possible role of each component known to be involved in the control of food intake, for the food intake depressing effect and altered dietary choice of animals fed disproportionate quantities of amino acids. The separate mechanisms of food intake control thought to be involved in the feeding of amino acid imbalanced or deficient diets, and diets containing amino acids in general excess (high protein diet) will be studied. The nature of possible receptor areas will be examined by bilateral electrolytic lesions in specific brain areas, implanting electrodes or cannulas and infusing amino acids or ammonia and following food intake responses with electronic recording balances. Detailed food intake patterns will be measured and examined using an on-line computerized electronic recording balance system so as to correlate the changes in metabolic events or metabolites with the changes in feeding pattern, thus attempting to establish cause-effect relationships among such changes.